ISO/IEC TS 18822:2015 defines a set of standard interfaces for C++ for dealing with file-system operations. This TS, which is based upon the Boost library's file-system implementation, is optional in C++17 and is now supported by the GCC C++ compiler.

I doubt we'll be using C++17 any time soon, considering we don't even use C++14 and only recently started using C++11. It'd be nice if we could start using C++14, though we'd almost certainly have to drop MSVC 2013 support for that.

MSVC always builds with the latest supported C++ version, so there's no switch to flip on there. It's just a case of starting to push C++14 code.

You know that you've reached c++14 territory (Or just full C++11 territory) once MSVC2013 builds start failing, at which point it's probably best to update the appveyor config to build with 2015 and 2017 instead